The present invention relates to a method for transferring rolls of soft paper grades, also known as tissue paper grades, that are rolled on core shafts to further processing. The invention also relates to an apparatus suitable for implementing the method.
In the art of papermaking, high bulk paper grades, also known as soft paper grades, are generally called tissue webs. Tissue webs also include silk paper grades. Tissue web finds particular use in various products requiring good absorbency, such as towels and napkins, diapers and the like. For these products, tissue web is subjected to further processing in order to make the absorbent pads or other liquid-receiving bulk portions needed in the final product. All of these raw material grades are characterized by high compressibility even under small compressive forces, as well as a low specific weight in regard to their volume.
Due to their high compressibility, the handling of tissue web rolls is difficult. It is desirable that the large specific volume of the product per unit weight be retained as unchanged as possible through all the manufacturing steps up to the end user in order to maintain the qualities of the product at an optimally high level. As such web rolls tend to collapse easily, the handling of the rolls must be carried out with maximum caution to roll damage so that the rolls are not subjected to high forces nor supported on their outer plies. One problem in the handling of rolls is associated with the removal of the set of parent rolls from the core shafts. In the production of soft tissue webs wider than about 5000 mm, the web leaving the papermaking machine is slit into two or more partial-width webs prior to winding, and the partial-width webs are wound onto individual cores on the core shafts to form a plurality of partial-width parent rolls. Prior to the start of the winding, the cores are already threaded onto the core shafts and thus the tissue paper rolls wound from the slit web have a width which is directly suitable for the further processing steps. Herein, a problematic phase occurs in the removal of the set of parent rolls from the core shaft. If the parent rolls are still supported by the core shaft on the reel rail, the core shaft cannot be pushed out from the rolls without an external support of the rolls. The friction between the core and the core shaft caused by the weight of the parent rolls resting on the shaft would prevent free sliding of the core shaft. In one prior-art method, this problem has been solved by supporting the parent rolls by their outer plies, whereby the weight of the rolls is relieved from resting on the core shaft. However, this arrangement involves the risk of reducing the caliper of the tissue web as a result of the externally applied forces from the weight of the rolls. Additional problems can result from the elasticity of the wound web causing the wound parent rolls to expand after the compressive pressure of the core shaft is removed. The winder of a prior-art arrangement is provided with a lift table that supports the parent roll and a downward sloped rolling ramp for transferring the rolls from the winder. For the handling of the core shaft, this apparatus construction is provided with core shaft puller means and other means for threading new cores onto a free shaft. Obviously, such supporting of the tissue web parent roll and the free rolling off the rolling ramp can readily degrade the compressibility properties of the tissue web and thus impair parent roll quality.
An object of the present invention is to provide a method and apparatus for supporting tissue parent rolls by their cores during their removal from the core shaft and, advantageously, also during their transfer to the further processing steps.
The goal of the invention, to remove the set of parent rolls from the core shaft while maintaining the quality of the wound paper, is achieved by supporting the core shaft at one end by a support such as a rail and at the other end by a roll change tube whose outer diameter is equal to that of the core shaft and whose end is operable to engage and support the end of the core shaft. When the core shaft is connected to the roll change tube, the rolls wound on the core shaft can be pushed onto the roll change tube outside the reel and then transferred to a pole truck pick-up position for further processing or storage.
The invention offers significant benefits. By virtue of the method, tissue parent rolls can be transferred so that they are supported by their cores in a continuous manner when they are pulled from the support of the core shaft, whereby there is no need to grab the roll or support the same by the outer plies of the roll. Hence, the risk of roll compression and damage can be eliminated from these steps of roll processing. The removal of parent rolls from the winder after being wound on a core becomes extremely fast and a new core shaft with the cores threaded thereon is rapidly placed into the vacant position of the just removed shaft. As the construction of the core-handling assembly is extremely uncomplicated, its cost as compared with its high roll-handling capacity remains very low. Furthermore, parent rolls removed from the core shaft can be handled by a lift truck having core chuck arms, whereby any post-processing of the rolls can be carried out without supporting the parent rolls by their outer plies.